2009 has 6 divisors (see below), whose sum is σ = 2394.
Its totient is φ = 1680.
The previous prime is 2003. The next prime is 2011. The reversal of 2009 is 9002.
Subtracting from 2009 its product of nonzero digits (18), we obtain a palindrome (1991).
Adding to 2009 its reverse (9002), we get a palindrome (11011).
It can be written as a sum of positive squares in only one way, i.e., 1225 + 784 = 35^2 + 28^2
It is not a de Polignac number, because 2009 - 24 = 1993 is a prime.
2009 is a modest number, since divided by 9 gives 2 as remainder.
It is a Curzon number.
It is a plaindrome in base 11 and base 15.
It is a nialpdrome in base 13.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (2003) by changing a digit.
It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 29 + ... + 69.
It is an arithmetic number, because the mean of its divisors is an integer number (399).
22009 is an apocalyptic number.
It is an amenable number.
2009 is a deficient number, since it is larger than the sum of its proper divisors (385).
2009 is an equidigital number, since it uses as much as digits as its factorization.
2009 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 55 (or 48 counting only the distinct ones).
The product of its (nonzero) digits is 18, while the sum is 11.
The square root of 2009 is about 44.8218696620.
The cubic root of 2009 is about 12.6180810371.
The spelling of 2009 in words is "two thousand, nine".